In patients with diabetes, glucose levels need to be monitored to maintain a healthy balance of glucose in the body. Glucose levels can be monitored by GBP coated sensors such as on-body CGM devices. On-body CGM devices generally include a light source used to illuminate or fluoresce GBP within a patient. These devices capture the light subsequently emitted by the GBP and analyze band wavelengths of the emitted light to determine the level of GBP. To identify GBP levels, a comparison can be made between the power of a reference band and the power of a signal band, which are both components of the light emitted by the GBP. The ratio of power of the reference band and the signal band is typically substantially proportional to the proportion of or level of glucose in the body of a patient.
Capturing and measuring the reference and signal bands of light emitted by a GBP has been accomplished by use of a series of lens and filters, which direct light to the GBP and attempt to separate the reference and signal bands prior to, or at a photodiode.
For example, existing CGM device designs attempt to capture the entire spectrum of light emitted by the GBP by both a reference photodiode and a signal photodiode. Each photodiode must then filter or block either the reference band or the signal band to accurately analyze GPB levels. As a result, less light is detected overall, because the light in the signal band that illuminates the reference band photodiode will not be detected, and the light in the reference band that illuminates the signal band photodiode likewise will not be detected. This inefficiency can dilute the analysis of the band wavelengths and can require greater initial light emission from a light source, requiring more energy and battery life.
Another prior CGM device design utilizes three separate glass filter components that must be individually placed and aligned during assembly to accurately reflect and transmit light from a light source to the GBP and from the GBP to a photodiode. This use of three distinct glass filters can add manufacturing and assembly costs and can increase the possibility of failure due to improper alignment of the glass filters. The use of three glass filter can also increase the overall size of the CGM device making it more inconvenient and uncomfortable for a user.
Another prior CGM design uses multiple filters positioned over a significant distance with respect to one another to direct the reference and signal bands to two different photodiodes. This filter configuration can lead to higher levels of stray light that is lost during transmission, thereby increasing light efficiency and decreasing the accuracy of the photodiode detecting the signal and reference bands.
With the CGM device designs above, there are concerns over light transmission inefficiencies, which contribute to the need for greater initial light emission, requiring greater power input/battery life. Additional concerns include manufacturing costs associated with the assembly of multiple components and the significant overall size of the CGM device.